Systems and methods herein generally relate to printing systems and more particularly systems that calibrate tone reproduction curves for different halftones.
As the number of color printers in common use has increased over the past decade, end users of such devices have become aware of the need to recalibrate these devices. Because of the nature of color reproduction, color printers are more subject to drift than are their black and white counterparts. One cause of such drift is deviation of the underlying components due to age or changes in the environment. For example, a typical color printing device is likely to vary due to changes in the underlying marking process in response to external conditions like temperature and humidity, and internal changes due to aging of the components. These variations from a known, standard state can result in undesirable variation in the appearance of the output from such reprographic devices. This may introduce various artifacts in the copy of the document produced by the output printer. For example, one or more portions of the copy may be too dark, too light, be shaded inaccurately, or include other artifacts. Compounding this problem of drift is the sensitivity of human perception, which, for certain colors, emphasizes even minor shifts or differences in color.
Common calibration methods include printing a test target and scanning it with a scanner that forms a part of the color reproduction device. The device compares the desired values with the values obtained from scanning the printed test target to calibrate the processing of image data to compensate for differences between the desired values and the values obtained from scanning the printed test target.
Printing systems targeted for non-graphic arts, low cost, and simple print production commonly offer multiple halftone states, where each halftone has a different, non-linear, “raw” or “native” response. The large development cost associated with developing a raster image processor (RIP) digital front end (DFE) that enables automated halftone tone reproduction curve (TRC)/profile matching make such RIP DFE's not cost effective for low cost systems.